Connecting pipe fitting of fuel cell and preparation method therefor, and fuel cell module

Abstract

The embodiments of the present application provide a connecting pipe fitting of a fuel cell and a preparation method therefor, and a fuel cell module. According to the connecting pipe fitting of the fuel cell in the embodiment of the present application, due to the fact that a first pipe and a third pipe are each made of a high-temperature alloy and are directly joined through a second pipe made of an insulating material, a thickness of a diffusion layer in a joint part is small, and the chemical stability is high; the connecting pipe fitting has the characteristic of high-temperature sealing insulation and is simple in preparation technology; and even under long-term high-temperature operating conditions, no micro-cracks are formed in the joint part, thus achieving good high-temperature mechanical properties and solving the problem of point leakage when running for a long time, such that the technical problem of a poor sealing effect caused by welding and mechanical sealing of a connecting pipe fitting of a fuel cell in the prior art is effectively solved, and technical support is provided for the commercial application of a fuel cell system.

Description

Fuel cell connecting pipe and preparation method thereof, and fuel cell module Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a connecting pipe fitting for a fuel cell, a preparation method thereof, and a fuel cell module. Background Art

[0002] A fuel cell is a chemical device that converts the chemical energy of a fuel directly into electrical energy. Because fuel cells convert the Gibbs free energy portion of the fuel's chemical energy into electrical energy through an electrochemical reaction, they are not subject to the limitations of the Carnot cycle and therefore have high efficiency. Fuel cells use fuel and oxygen as raw materials and lack mechanical transmission components, resulting in zero noise pollution and minimal harmful gas emissions, minimizing environmental pollution.

[0003] Fuel cells include phosphoric acid fuel cells, alkaline fuel cells, proton exchange membrane fuel cells, molten carbonate fuel cells, solid oxide fuel cells, direct methanol fuel cells, etc. These fuel cells all work on the same principle and are categorized based on the type of fuel used, driving temperature, catalyst, etc.

[0004] A fuel cell power generation system usually contains two or more fuel cells. Each fuel cell stack needs to be connected and gas transported through pipes. The connecting pipes must have good sealing performance. To prevent short circuits between the positive and negative poles of the fuel cell stack during use, the connecting pipes between the fuel cell stacks must have relevant insulation properties. At the same time, to meet the characteristics of some models of fuel cells working at high temperatures, the connecting pipes must also have the characteristics of not generating microcracks or air leakage in the sealing area under high-temperature operating conditions (600-800℃) for a long time.

[0005] Summary of the Invention

[0006] The present invention provides a connecting pipe for a fuel cell and a preparation method thereof in order to solve at least one of the problems existing in the prior art.

[0007] A first aspect of the present invention provides a connecting pipe for use in a fuel cell. The connecting pipe of the present invention comprises:

[0008] a first tube having a first lumen;

[0009] a second tube, wherein a first end of the second tube is connected to the first end of the first tube, the second tube having a second cavity, the second cavity being in communication with the first cavity;

[0010] a third tube, wherein a first end of the third tube is connected to the second end of the second tube, the third tube having a third cavity, the third cavity being in communication with the second cavity;

[0011] The first tube and the third tube are both made of high-temperature metal;

[0012] The second tube is made of insulating material;

[0013] The first tube and the third tube are connected through the second tube.

[0014] In some embodiments of the present application, an interface formed by the bonding of the first tube and the second tube, and the third tube and the second tube has a diffusion layer, and the thickness of the diffusion layer is no more than 50 μm.

[0015] In some embodiments of the present application, the diffusion layer has a thickness of 0-20 μm;

[0016] In some embodiments of the present application, the diffusion layer has a thickness of 0-1 μm.

[0017] In the present invention, the first tube and the third tube are directly joined via the second tube, and no additional transition layer is required at the joint surface. This reduces the number of sealing surfaces and improves reliability. After sealing, the first tube, the second tube, and the third tube are all in a highly stable state (after long-term use, the thickness of the diffusion layer changes little), and have high chemical stability. The first tube, the third tube, and the second tube will not chemically react at high temperatures, and the sealing will not fail after long-term use due to diffusion of interface elements or related chemical reactions.

[0018] The diffusion layer gradually increases with the increase of usage time, but the maximum thickness does not exceed 50 μm.

[0019] In some embodiments of the present application, the difference in thermal expansion coefficient between the insulating material and the metal material is 0-2×10 -6 K -1 , which can reduce the stress influence during the sealing process and achieve matching sealing of insulating materials and metal materials.

[0020] In some embodiments of the present application, the insulating material includes a ceramic material.

[0021] In some embodiments of the present application, the insulating material is glass-ceramics.

[0022] In some embodiments of the present application, the high-temperature metal is a high-temperature alloy.

[0023] In some embodiments of the present application, the first tube and / or the third tube is a flanging tube.

[0024] In some embodiments of the present application, the flange extends toward the outside or inside of the tube.

[0025] In some embodiments of the present application, the flange length is 0-50 mm;

[0026] In some embodiments of the present application, the flange length is 2-10 mm;

[0027] In some embodiments of the present application, the length of the flanging tube is 4-5 mm;

[0028] In some embodiments of the present application, the flange thickness of the flanged tube is 0-5 mm;

[0029] In some embodiments of the present application, the flange thickness of the flanged tube is 0.1-2 mm;

[0030] In some embodiments of the present application, the flange thickness of the flanged tube is 0.2-0.4 mm;

[0031] In some embodiments of the present application, the first end of the second tube has a first groove, and the first end of the first tube is embedded in the first groove;

[0032] and / or,

[0033] The second end of the second tube has a second groove, and the first end of the third tube is embedded in the second groove.

[0034] In some embodiments of the present application, the first end of the second tube has a first boss, and the first boss is inserted into the first end of the first tube;

[0035] and / or,

[0036] The second end of the second tube has a second boss, and the second boss is inserted into the first end of the third tube.

[0037] In some embodiments of the present application, the first tube and / or the third tube are in the shape of a bellows.

[0038] A second aspect of the present invention provides a method for preparing the connecting pipe, the method comprising:

[0039] forming a second tube through an insulating material;

[0040] The first tube and the third tube are formed by high temperature metal;

[0041] The first end of the second tube is brought into contact with the first end of the first tube, and the second end of the second tube is brought into contact with the first end of the third tube, and then heated to the crystallization temperature of the second tube in an air atmosphere, so that the first tube and the third tube are joined together through the second tube.

[0042] A third aspect of the present invention provides a fuel cell module, which includes at least two fuel cell stacks and the above-mentioned fuel cell connecting pipe fittings, and the fuel cell stacks are connected by the connecting pipe fittings.

[0043] The beneficial effects of the embodiments of the present invention are:

[0044] The connecting pipe fitting of the fuel cell described in the embodiment of the present invention has a low diffusion layer thickness in the joint portion and high chemical stability, because the first pipe and the third pipe are both made of high-temperature metal and are directly joined by the second pipe made of insulating material. The manufacturing process is simple, and even when operated under long-term high-temperature conditions, no microcracks are generated in the joint portion. The high-temperature mechanical properties are good, and no point leakage occurs during long-term operation. This effectively solves the technical problem of poor sealing effect of connecting pipe fittings for fuel cells in the prior art due to welding and mechanical sealing, and provides technical support for the commercial application of fuel cell systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without any creative work.

[0046] FIG1 is a first structural schematic diagram of a connecting pipe member for a fuel cell provided by an embodiment of the present invention;

[0047] FIG2 is a second structural schematic diagram of a connecting pipe member for a fuel cell provided by an embodiment of the present invention;

[0048] FIG3 is a third structural schematic diagram of a connecting pipe fitting for a fuel cell provided by an embodiment of the present invention;

[0049] FIG4 is a fourth structural schematic diagram of a connecting pipe member for a fuel cell provided by an embodiment of the present invention;

[0050] FIG5 is a fifth structural schematic diagram of a connecting pipe fitting for a fuel cell provided by an embodiment of the present invention;

[0051] FIG6 is a sixth structural schematic diagram of a connecting pipe fitting for a fuel cell provided by an embodiment of the present invention;

[0052] FIG. 7 is a seventh structural schematic diagram of a connecting pipe fitting for a fuel cell provided in an embodiment of the present invention.

[0053] in:

[0054] 100, first tube; 101, first cavity; 200, second tube; 201, second cavity; 202, first groove; 203, first boss; 204, second boss; 205, second groove; 300, third tube; 301, third cavity. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0056] In the description of the embodiments of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they should not be understood as limiting the embodiments of the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0057] In the description of the embodiments of the present application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," and "joined" should be understood in a broad sense. For example, they may refer to fixed connections, replaceable connections, or integral connections. They may refer to mechanical connections or electrical connections. They may refer to direct connections or indirect connections through an intermediate medium. They may refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of the present application according to specific circumstances.

[0058] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0059] Example 1

[0060] As shown in FIG1 , FIG1 is a first structural schematic diagram of a connecting pipe member for a fuel cell provided by an embodiment of the present invention;

[0061] As shown in Figures 1-7, an embodiment of the present invention provides a connecting pipe fitting for a fuel cell, the connecting pipe fitting comprising:

[0062] A first tube 100 having a first cavity 101;

[0063] A second tube 200 , wherein a first end of the second tube 200 is connected to a first end of the first tube 100 , and the second tube has a second cavity 201 , and the second cavity 201 is in communication with the first cavity 101 ;

[0064] A third tube 300 , wherein a first end of the third tube 300 is connected to a second end of the second tube 200 , and the third tube 300 has a third cavity 301 , which is in communication with the second cavity 201 ;

[0065] Specifically, the first tube 100 , the second tube 200 and the third tube 300 are connected through the second tube 200 .

[0066] The first end surface of the second tube 200 has a first bonding interface, and the second end surface of the second tube 200 has a second bonding interface, wherein the first end surface of the first tube 100 is bonded to the first bonding interface. The first end surface of the third tube 300 is bonded to the second bonding interface.

[0067] The diffusion layers of the first bonding interface and the second bonding interface are no larger than 50 μm.

[0068] Preferably, the thickness of the diffusion layer is 0-20 μm. More preferably, the thickness of the diffusion layer is 0-1 μm. The first tube 100 and the third tube 300 are directly joined through the second tube 200, and no additional transition layer is required on the joint surface. The number of sealing surfaces is small and the reliability is high. After sealing, the first tube 100, the second tube 200, and the third tube 300 are all in a highly stable state (after long-term use, the thickness of the diffusion layer changes little), with high chemical stability. The first tube 100, the third tube 300, and the second tube 200 will not chemically react at high temperatures, and the sealing will not fail after long-term use due to diffusion of interface elements or related chemical reactions. The diffusion layer gradually increases with the increase of use time, but the maximum thickness does not exceed 50 μm.

[0069] Wherein, the first tube 100 and the third tube 300 are both made of high-temperature metal;

[0070] The high-temperature metal is a high-temperature alloy, which includes an iron-based alloy, a nickel-based alloy or other metal alloys with high-temperature oxidation resistance, such as SUS310s, SUS316s, SUS444, SUS430, SUS410, inconel600, inconel625 and GH3030;

[0071] The second tube 200 is made of insulating material.

[0072] Preferably, the insulating material of the second tube 200 comprises a ceramic material;

[0073] More preferably, the insulating material of the second tube 200 is glass-ceramics. The main crystalline phase in the glass-ceramics portion includes at least one of magnesia, feldspar, olivine, calcite, silica, cerium dioxide, lanthanum aluminum borate, and calcium lanthanum borate.

[0074] When the microcrystalline glass portion contains magnesia chalcedony and silica crystal phases, the ratio of the two crystal phases needs to satisfy magnesia chalcedony / silicon dioxide = 0.3-8; when the microcrystalline glass portion contains feldspar and silica crystal phases, the ratio of the two crystal phases needs to satisfy feldspar / silicon dioxide = 0.3-5; when the microcrystalline glass portion contains magnesia chalcedony and olivine, the ratio of the two crystal phases needs to satisfy magnesia chalcedony / olivine = 0-15.

[0075] The high temperature alloy matches the thermal expansion coefficient of the insulating material.

[0076] Preferably, the difference in thermal expansion coefficient between the insulating material and the metal material is 0-2×10 -6 K -1 .

[0077] As shown in Figure 1, preferably, the first cavity 101, the second cavity 201, and the third cavity 301 have the same inner diameter. This facilitates a smooth transition between the first cavity 101, the second cavity 201, and the third cavity 301 after the first tube 100, the second tube 200, and the third tube 300 are joined, allowing the gas therein to pass more smoothly without causing changes in the airflow. Furthermore, the first tube 100, the second tube 200, and the third tube 300 have the same inner diameter, allowing them to better align when joined together, without forming a stepped shape after joining.

[0078] As shown in Figure 5, to facilitate manufacturing, the first tube 100 and the third tube 300 are made of the same material, structure, and dimensions. This allows them to be directly processed without separate machining. Alternatively, the first tube 100 and the third tube 300 are made of the same high-temperature alloy, ensuring they have the same thermal expansion coefficient. Alternatively, the first tube 100 and the third tube 300 have the same inner diameter and the same outer diameter; the first tube 100 and the third tube 300 can be manufactured using the same mold.

[0079] In other embodiments, the first tube 100 and the third tube 300 may be of different sizes, materials or structures, which may be selected and adjusted according to actual needs.

[0080] The connecting pipe fittings for the fuel cell described in the embodiment of the present application have high-temperature sealing and insulating properties because the first tube 100 and the third tube 300 are both made of high-temperature alloys, and the second tube 200 is made of an insulating material. The second tube 200 is directly joined by the insulating material of the second tube 200. The manufacturing process is simple, and even when operated under long-term high-temperature conditions, no microcracks are generated in the joints. The high-temperature mechanical properties are good, and no point leakage occurs during long-term operation. This effectively solves the technical problem of poor sealing effect of connecting pipe fittings for fuel cells in the prior art due to welding and mechanical sealing, and provides technical support for the commercial application of fuel cell systems.

[0081] As shown in Figure 3, in some embodiments of the present application, the first tube 100 and / or the third tube 300 are flanged tubes. Specifically, the first end of the first tube 100 and / or the first end of the third tube 300 are flanged and extended outward.

[0082] These include three situations: the first end of the first tube 100 extends outwardly with a flange, the first end of the third tube 300 extends outwardly with a flange, or both the first end of the first tube 100 and the first end of the third tube 300 extend outwardly with a flange. This outward flange extension design allows the first tube 100 and the third tube 300 to have a larger contact surface with the second tube 200, facilitating engagement. Of course, there are also three situations: the first end of the first tube 100 extends inwardly with a flange, the first end of the third tube 300 extends inwardly with a flange, or both the first end of the first tube 100 and the first end of the third tube 300 extend inwardly with a flange. As shown in FIG4 , in some embodiments of the present application, the first tube 100 and / or the third tube 300 are shaped like a corrugated tube.

[0083] These include three situations: the shape of the first tube 100 is a corrugated tube, the shape of the third tube 300 is a corrugated tube, and the shapes of the first tube 100 and the third tube 300 are both corrugated tubes.

[0084] The bellows-shaped design allows the first tube 100 and / or the third tube 300 to deform before other components, thereby buffering and releasing stress, thereby protecting other components of the fuel cell stack from deformation or even damage due to external forces.

[0085] As shown in FIG. 2 and FIG. 7 , in some embodiments of the present application, the first end of the second tube 200 has a first groove 202 , and the first end of the first tube 100 is embedded in the first groove 202 ;

[0086] and / or,

[0087] The second end of the second tube 200 has a second groove 205 , and the first end of the third tube 300 is embedded in the second groove 205 .

[0088] The first end of the first tube 100 is embedded in the first groove 202 for installation, so that no additional fixation is required. When heated, the second tube 200 can be heated to the crystallization temperature, thereby being joined with the first tube 100, with good joining effect and high joining efficiency. Similarly, the second groove 205 can also enable the third tube 300 to be effectively joined without additional fixation.

[0089] As shown in FIG6 , in some embodiments of the present application, the first end of the second tube 200 has a first boss 203 , and the first boss 203 is inserted into the first end of the first tube 100 ;

[0090] and / or,

[0091] The second end of the second tube 200 has a second boss 204 , and the second boss 204 is inserted into the first end of the third tube 300 .

[0092] The second tube 200 has a boss to control the coaxiality of the entire tube to meet the assembly accuracy requirements.

[0093] In other embodiments, the first tube 100 , the second tube 200 , and the third tube 300 can be combined according to actual needs.

[0094] An embodiment of the present invention further provides a method for preparing a connecting pipe for a fuel cell, the method comprising:

[0095] The second tube 200 is made of insulating material;

[0096] The first tube 100 and the third tube 300 are made of high-temperature metal;

[0097] The first end of the second tube 200 is brought into contact with the first end of the first tube 100, and the second end of the second tube 200 is brought into contact with the first end of the third tube 300. The tubes are then heated to the crystallization temperature of the second tube 200 in an air atmosphere to crystallize the insulating material. The mixture is sintered for more than 0.5 hours, so that the first tube 100, the second tube 200, and the third tube 300 are bonded together via the second tube 200.

[0098] A mold or a tool is used to place the high-temperature metal and the insulating material in the mold or the tool, and then heat and sinter them, so that the first tube 100, the second tube 200, and the third tube 300 are integrally formed.

[0099] The first end of the second tube 200 has a first groove 202, and the first end of the first tube 100 is inserted into the first groove 202; the second end of the second tube 200 has a second groove 205, and the first end of the third tube 300 is inserted into the second groove 205. Sintering is performed so that the first tube 100, the second tube 200 and the third tube 300 are joined together through the second tube 200.

[0100] Alternatively, the first end of the first tube 100 extends outwardly with a flange, and this end contacts the first end of the second tube 200. The first end of the third tube 300 extends outwardly with a flange, and the flange portion contacts the second end of the second tube 200. Through direct contact sintering, the first tube 100, the second tube 200, and the third tube 300 are joined together through the second tube 200.

[0101] In the following embodiment of the connecting pipe fitting, the first pipe 100 is made of a high-temperature alloy material, the second pipe 200 is made of a microcrystalline glass, and the third pipe 300 is made of a high-temperature alloy material. The thermal expansion coefficient of the microcrystalline glass is controlled within (11±0.5)×10 -6 K -1 If the dimensions of the following glass-ceramic tubes are not specified, the dimensions of the glass-ceramic tubes are 24 mm in inner diameter, 32 mm in outer diameter, and 14 mm in height. The high-temperature alloys used in the first tube 100 and the third tube 300 are both ferritic stainless steel SUS444 (Note: The thermal expansion coefficient of SUS444 is (11×10 -6 K -1 ).

[0102] The differences between Example 25 and Example 26 and Example 21 are:

[0103] In Example 25, the metal material used for the first and third tubes is SUS430;

[0104] The metal material used for the first tube and the third tube in Example 26 is SUS410.

[0105] Comparative Example

[0106] Performance test and qualification standards:

[0107] 1. Thermal shock test (thermal shock resistance): 5℃ / min heating and cooling, 800℃ holding for 2 hours, 20 cycles, no abnormality in product appearance; normal temperature air leak detection, pressure maintenance 6000Pa, leakage less than 10Pa / min;

[0108] 2. Aging performance test (high temperature reliability): 1℃ / min heating and cooling, 800℃ heat preservation for 2000h, no abnormality in product appearance; normal temperature air leak detection, pressure maintenance 6000Pa, leakage less than 10Pa / min;

[0109] 3. High temperature voltage resistance and insulation properties: can withstand 1000V voltage continuously applied for at least 15s, the voltage value remains stable; the resistivity is greater than 1×10 4 Ω·cm;

[0110] 4. High temperature mechanical properties: Under high temperature conditions of 800℃, it can withstand at least 40N of tensile force and 15N of shear force without leakage;

[0111] 5. Diffusion layer test method of bonding interface: XRD combined with EPMA is used for testing.

[0112] The fuel cell connecting pipe fitting of the present invention has high-temperature sealing and insulation properties and a simple preparation process. The high-temperature alloy matches the thermal expansion coefficient of the microcrystalline glass, and the second tube 200 is joined to the first tube 100 and the third tube 300 through the second tube 200. Even when operated under long-term high-temperature conditions, no microcracks are generated at the joint. The high-temperature mechanical properties are good, and no point leakage occurs during long-term operation, providing technical support for the commercial application of fuel cells.

[0113] In addition, this embodiment also provides a fuel cell module comprising at least two fuel cell stacks and the aforementioned fuel cell connecting pipes, with the fuel cell stacks connected by the connecting pipes. Compared with the prior art, this fuel cell module has advantages such as good sealing and low leakage.

[0114] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A connecting pipe for a fuel cell, characterized in that: The connecting pipe comprises: a first tube having a first lumen; a second tube, wherein a first end of the second tube is connected to a first end of the first tube, the second tube has a second cavity, and the second cavity is in communication with the first cavity; a third tube, a first end of the third tube being connected to the second end of the second tube, the third tube having a third cavity, the third cavity being in communication with the second cavity; Wherein, the first tube and the third tube are both made of high-temperature metal; The second tube is made of insulating material; The first tube and the third tube are connected through the second tube.

2. The fuel cell connecting pipe according to claim 1, characterized in that: An interface formed by the joining of the first tube and the second tube, and the third tube and the second tube has a diffusion layer, and the thickness of the diffusion layer is not greater than 50 μm.

3. The connecting pipe of the fuel cell according to claim 1, characterized in that: The difference in thermal expansion coefficient between the insulating material and the metal material is 0-2×10 -6 K -1 .

4. The connecting pipe of the fuel cell according to claim 1, characterized in that: The insulating material includes a ceramic material.

5. The connecting pipe of the fuel cell according to claim 1, characterized in that: The first tube and / or the third tube are / is a flanged tube.

6. The connecting pipe of the fuel cell according to claim 5, characterized in that: The flange extends toward the outside or inside of the tube, and preferably the flange length is 0-50 mm; the flange thickness of the flanged tube is 0-5 mm.

7. The connecting pipe of the fuel cell according to claim 1, characterized in that: The first end of the second tube has a first groove, and the first end of the first tube is embedded in the first groove; and / or, The second end of the second tube has a second groove, and the first end of the third tube is embedded in the second groove.

8. The connecting pipe of the fuel cell according to claim 1, characterized in that: The first end of the second tube has a first boss, and the first boss is inserted into the first end of the first tube; and / or, The second end of the second tube has a second boss, and the second boss is inserted into the first end of the third tube.

9. A method for preparing a fuel cell connecting pipe, characterized in that: The preparation method comprises: forming a second tube through an insulating material; The first tube and the third tube are formed by high temperature metal; The first end of the second tube is brought into contact with the first end of the first tube, and the second end of the second tube is brought into contact with the first end of the third tube, and then heated to the crystallization temperature of the second tube in an air atmosphere, so that the first tube and the third tube are joined together through the second tube.

10. A fuel cell module, characterized in that: It comprises at least two fuel cell stacks and a connecting pipe fitting of a fuel cell as claimed in any one of claims 1 to 8, wherein the fuel cell stacks are connected via the connecting pipe fitting.

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